Carbon fiber based tubing encapsulated cable

ABSTRACT

Tubing encapsulated cable consists of one or more electrical conductors and possibly one or more fiber optic cables sheathed in a corrosion resistant metallic alloy. However, pumping during the installation of tubing encapsulated cable is required to overcome the capstan effect of the tubing encapsulate cable inside the coil tubing as the tubing encapsulated cable travels through the coiled up wraps of coil tubing. In an embodiment of the invention the tubing encapsulated cable consists of one or more electrical conductors and possibly one or more fiber optic cables sheathed in a fiber reinforced composite sheath. Because there is little drag between the fiber encapsulated cable and the coil tubing, conventional pumping operations used to install braided wireline into coil tubing may not be required when installing fiber encapsulated cable into coil tubing. Additionally, the smooth outside surface and relatively small diameter of the fiber encapsulated cable are desirable attributes for well intervention work because the smooth surface is more resistant to chemical attack than braided wire while the smooth surface and relatively small diameter provide little viscous drag while fluids are pumped through the coil tubing in the course of intervention operations.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Patent ApplicationNo. 61/921,436 that was filed on Dec. 28, 2013, and to U.S. patentapplication No. 14/564,894 filed on Dec. 9, 2014.

BACKGROUND

Tubing encapsulated cable can be difficult to insert into coil tubing.Tubing encapsulated cable typically consists of one or more electricalconductors, a fiber optic cable, and possibly other cables or linessheathed in a corrosion resistant alloy such as 316 stainless steel or afiber reinforced composite sheath. The smooth outside surface andrelatively small diameter of tubing encapsulated cable are desirableattributes for well intervention work because the relatively smoothsurface may be more resistant to chemical attack than braided wire.Additionally, the relatively smooth surface and small diameter(0.125″-0.250″) minimizes viscous drag exerted upon the cable as fluidspumped through the coil tubing in the course of intervention operationspass by the cable. Because there is little drag on the tube wire,conventional pumping operations used to install braided wireline intocoil tubing are not sufficient to install tubing encapsulated cable.Pumping fluid through the coil tubing during the installation of tubingencapsulated cable is required to assist in overcoming the capstaneffect, caused by the friction between the coil tubing and the tubingencapsulated cable as the tubing encapsulated cable travels through thewound coil tubing.

There are numerous techniques that may be utilized to install tubingencapsulated cable into a long tubular member such as coil tubing. Suchas hanging the coil into the well in order to allow the somewhatreliable force of gravity to pull the tubing encapsulated cable downwardinto the interior of the coil tubing. Another commonly known techniqueinvolves, prior to utilizing the coil tubing downhole, spooling out thecoil tubing along a roadway, installing a rope, cable, or equivalent andusing the rope or cable in a manner similar to that of an electrician'sfish tape to pull the tubing encapsulated cable into the coil tubing. Inthese instances fluid may or may not be pumped into the coil tubingwhile inserting the tubing encapsulated cable. Inserting the tubingencapsulated cable into coil tubing as described above can be anexpensive operation. Wire and cable have been used with a tubularconduit since the late 1800s, conduit, like coil tubing, is a longtubular member that normally has wires and cables with a wide variety ofouter armors run through it.

Another currently utilized method of installing tubing encapsulatedcable into coil tubing is while pumping fluid through the coil tubing toattach a plug to the end of the tubing encapsulated cable. The plug willthen pull the tubing encapsulated cable through the coil tubing as theplug is pumped through the coil tubing.

One problem of using a conventional tubing encapsulated cable is thatsuch cables typically have a metallic outer sheath, in particular theyusually have a stainless steel outer sheath. When the tubingencapsulated cable outer sheath is a metal that is dissimilar to themetal used to manufacture the coil tubing electrolytic corrosion may bean issue.

SUMMARY

One solution to the problem of electrolytic corrosion between the coiltubing and the tubing encapsulated cable is to replace the metallicouter sheath with plastic or composite fiber wrapped around the innerelectrical conductors, a fiber optic cable, communication lines, orother cables.

In one embodiment a carbon fiber composite tube may be formed around aninner core that may consist of one or more electrical conductors orfiber optic cables or some combination of electrical conductors andfiber optic cables. The carbon fiber composite tubing may be formedaround the inner core by a continuous braiding process where independentstrands of fiber are spirally braided together to form a tube thatencapsulates the inner core. In many instances after the carbon fibercomposite tubing is formed around the inner core the carbon fiber outersheath may be impregnated with an epoxy or other binder. Such a tube maybe created in any length desired but preferably of such a length as tomatch the length of the coil tubing, plus about ten percent, that thecarbon fiber wrapped core will be installed in.

In an alternative embodiment an inner core such as a communications lineor a cable may be laid over the top of a flat length of pre-woven carbonfiber such a length of carbon fiber cloth. The pre-woven carbon fibermay then by rolled into a tubular or other shape to encapsulate theinner core. The now adjoining edges of the pre-woven carbon fiber maythen be attached by various means including sewing the edges together,by using an adhesive such as an epoxy to bond the edges of the pre-wovencloth together, or by impregnating the carbon fiber outer sheath withepoxy or other binder or adhesive.

In another embodiment the fiber encapsulated cable for use is installedin coil tubing. A conductor may be at least a first conductor and asecond conductor. The first conductor may be an electrical conductor andthe second conductor may be an optical conductor. In certain instancesthe conductor may have a coating and that coating may be an insulator. Acarbon fiber sheath wraps around the conductor and the carbon fibersheath typically has a low coefficient of friction between the coiltubing and the carbon fiber sheath as the sheath is pulled along theinterior surface of the coil tubing. The fiber sheath may be resinimpregnated. A filler may separate the conductor from the fiber sheath.In certain instances the filler may be electrically conductive orelectrically insulative. Typically the fiber encapsulated cable ispulled through the coil tubing in order to insert the fiber encapsulatedcable into the coil tubing without pumping a fluid through the coiltubing.

In another embodiment the fiber encapsulated cable may be installedwithin a pipeline. In other embodiments the fiber encapsulated cable maybe strapped to the exterior of the pipeline, buried alongside thepipeline, or otherwise placed in conjunction with the pipeline.

In certain instances the fiber encapsulated cable may, either inaddition to other conductors within the fiber encapsulated tubing or inplace of such conductors, be electrically conductive. The fiberencapsulated cables electrical transmission capabilities may be used tosupply electrical power to remote locations. Such locations may use theelectrical power to supply remote communities or to supply power toremote locations for use in conjunction with the pipeline. For instancethe fiber encapsulated cable may be used to supply power to rectifiersat remote locations. In turn the rectifiers power anodes which allowsfor cathodic protection in a metal pipeline.

It has also been found that by having a fiber encapsulated tubing withan optical conductor within the pipeline it is possible to takeadvantage of the myriad sensing capabilities of optical conductors toallow pipeline monitoring. For example the variations in thetemperature, such as temperature changes due to expanding gas from aleak in a pipeline, may be detected by an optical conductor within afiber encapsulated cable. The optical fiber expands or contracts due tolocal temperature variations and such changes in the length of theoptical conductor may be detected and pinpointed by the pipelineoperator. Early detection of leaks enables the pipeline operator tominimize product losses and potential environmental damage. In anotherexample, local vibrations may be detected and located along the lengthof a pipeline having an optical conductor within the fiber encapsulatedcable. Such vibrations may indicate heavy equipment or digging near thepipeline thereby allowing the pipeline operator to intervene prior tothe pipeline being damaged. In another example the variations in localpipeline pressure, such as local pressure changes due to obstructions,corrosion, external damage to the pipeline, may be detected by anoptical conductor within a fiber encapsulated cable. The optical fiberexpands or contracts due to local pressure variations and such changesin the length of the optical conductor may be detected and pinpointed bythe pipeline operator. Early detection of damage again enables thepipeline operator to minimize product losses and potential environmentaldamage.

Conventional wireline or metallic tubing encapsulated cable has poorcorrosion resistance. Because the encapsulation material of thisalternative embodiment is not metallic, no electrolytic relatedcorrosion of the coil tubing, the pipeline, or the cable can take place.Additionally, carbon fiber is typically inert and is less susceptible todamage by wellbore fluids or fluids flowing through a pipeline.

Conventional wireline or metallic tubing encapsulated cable isrelatively heavy requiring slack management. Slack management includesperiodic back pumping fluid through the coil tubing. However, carbonfiber encapsulated cable is relatively lightweight and tends to reducethe overall weight of the tubing encapsulated cable when compared toconventional wireline or metallic tubing encapsulated cable. Such areduction in weight reduces the requirement of managing any slack in theline as the tubing encapsulated cable is run into the coil tubing.Additionally, the low viscous drag of tubing encapsulated cable due toits relatively small diameter and consequent low surface area togetherwith an appropriately engineered outer surface, that also reduces theweight, greatly reduce the need for slack management and back pumpingoperations.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts a fiber encapsulated cable having a number of conductorswrapped in a carbon fiber sheath.

FIG. 2 depicts the fiber encapsulated cable after it has been installedin a coil tubing.

FIG. 3 depicts a fiber encapsulated cable having an inner sheath and afiber outer armor sheath.

FIG. 4 depicts a fiber encapsulated cable having an inner sheath and anouter electrical isolation layer that chemically protects the innerlayers from treating fluids as well as wellbore fluids.

FIG. 5 depicts a fiber encapsulated cable having a single conductor.

DETAILED DESCRIPTION

The description that follows includes exemplary apparatus, methods,techniques, or instruction sequences that embody techniques of theinventive subject matter. However, it is understood that the describedembodiments may be practiced without these specific details.

FIG. 1 depicts an embodiment of the present invention where a fiberencapsulated cable 10 has a number of conductors wrapped in a carbonfiber sheath 12. While the carbon fiber sheath 12 is shown, other typesof fiber, such as fiberglass, may be used. Depending upon the propertiesof the carbon fiber the carbon fiber sheath may be either an electricalinsulator or an electrical conductor. Usually the carbon fiber iscombined with a resin as the carbon fiber sheath 12 is formed around theinner core of conductors, coatings, and pliable material. The fiberencapsulated cable 10 may have any number of conductors, such as thethree conductors 14, 16, and 18 shown, where each conductor 14, 16, or18 may have a coating 20, 22, or 24 that may be an insulator, an opticalcoating, a bonding layer, a protective layer against corrosion or otherdegradation, or other material depending upon the requirements for thefiber encapsulated cable 10. Multiple coating layers may be used foreach conductor. In many instances the optical conductor may be coatedwith an electrical conductor while an electrical conductor may be coatedwith an electrical insulator. A carbon fiber may be used as a coating20, 22, or 24 and depending upon the fiber's properties could be eitheran electrical insulator or a conductor. In many instances it isdesirable to embed the conductors 14, 16, and 18 and their coatings 20,22, and 24 in a pliable material 26. The pliable material 26 may providesupport for the carbon fiber sheath 12. The pliable material 26 alsoprovides additional protection from mechanical or chemical damage to theconductors 14, 16, and 18 and their coatings 20, 22, and 24. The pliablematerial 26 may also be used as an additional conductor depending uponthe properties of the material used for the pliable material 26. In mostinstances the pliable material 26 will be a carbon fiber matrixcomprised of strands of carbon fiber and/or carbon nano-tubes in apolymer matrix that bonds the matrix together although the pliablematerial could be a simple polymer or plastic material.

In FIG. 1 the tubing encapsulated cable may be constructed by fixing oneor more coatings 20, 22, or 26 onto a conductor 14, 16, or 18. In someinstances a conductor may not have a coating. The conductors 14, 16, and18 and their respective coatings 20, 22, and 24 are then bound togetherin the pliable material 26 to form the inner core. The carbon fibersheath 12 may be spiral wound onto the inner core although in someinstances the carbon fiber sheath may be formed from a pre-woven matthat is then folded over the inner core so that the pre-woven mat'sedges overlap and are then held in place by resin or some otheradhesive. In other instances the pre-woven mat may be spiral wrappedaround the inner core.

FIG. 2 depicts the fiber encapsulated cable 10 of FIG. 1 after it hasbeen installed in a coil tubing 30. In many instances the fiberencapsulated cable 10 may be installed in the coil tubing 30 by pullingthe fiber encapsulated cable 10 through the interior of the coil tubing30. The fiber encapsulated cable 10 is especially suitable for beingpulled through the interior of the coil tubing 30 as the carbon fibersheath 12 fiber tends to have a high tensile strength making it suitablefor being pulled. The carbon fiber sheath 12 also tends to have a lowfriction coefficient as compared to a metal encapsulated cable. The lowfriction between the coil tubing 30 and the carbon fiber sheath 12 ofthe fiber encapsulated cable 10 reduces the capstan effect between thecoil tubing 30 and the fiber encapsulated cable 10 as the fiberencapsulated cable 10 is pulled around bends and curves in the coiltubing 30 and generally reduces the friction between longs lengths ofthe fiber encapsulated cable 10 and the coil tubing 30 as the carbonfiber sheath 12 rubs against the interior of the coil tubing 30.

FIG. 3 depicts an alternative embodiment of a fiber encapsulated cable50. In this embodiment the fiber encapsulated cable 50 has at least oneinner conductor and in this embodiment two inner conductors 54 and 56.Each conductor 54 and 56 may be electrically or optically conductive. Inthe fiber encapsulated cable 50 the conductors may be of differenttypes, for example conductor 54 may be electrically conductive whileconductor 56 may be optically conductive. Each inner conductor 54 and 56may have an outer coating 58 and 60. The conductors 54 and 56 as well astheir respective coatings 58 and 60 may then be encapsulated in apliable material 61. In certain instances the pliable material 61 is notnecessary and the conductors 54 and 56 as well as their respectivecoatings 58 and 60 may be wrapped by a first sheath 62. In otherinstances the pliable material 61 may harden over a preset period oftime such that the pliable material may harden after installation in thecoil tubing. The first sheath may be a fiber sheath, such as carbonfiber but may be a metal sheath as well. An intervening layer 64surrounds and protects the conductors 54 and 56, coatings 58 and 60, andfirst sheath 62. The intervening layer 64 may be electrically conductiveand may be a carbon fiber matrix comprised of strands of carbon fiberand/or carbon nano-tubes in a polymer matrix that bonds the matrixtogether although the pliable material could be a simple polymer orplastic material. An outer armor layer 52 may be resin impregnatedcarbon fiber or some other fiber as is known in the industry.

FIG. 4 depicts an alternative embodiment of a fiber encapsulated cable70. In this embodiment the fiber encapsulated cable 70 has at least oneand in this embodiment two inner conductors 74 and 76. Each conductor 74and 76 may be electrically or optically conductive. In a single fiberencapsulated cable 70 the conductors may be of different types, forexample conductor 74 may be electrically conductive while conductor 76may be optically conductive. Each inner conductor 74 and 76 may have anouter coating 78 and 80. The conductors 74 and 76 as well as theirrespective coatings 78 and 80 may then be encapsulated in a pliablematerial 88. In certain instances the pliable material 88 is notnecessary and the conductors 74 and 76 as well as their respectivecoatings 78 and 80 may be wrapped by a first sheath 82. The first sheathmay be a fiber sheath, such as carbon fiber but may be a metal sheath aswell. An intervening layer 84 surrounds and protects the conductors 74and 76, coatings 78 and 80, and first sheath 82. The intervening layer84 may be electrically conductive and may be a carbon fiber matrixcomprised of strands of carbon fiber and/or carbon nano-tubes in apolymer matrix that bonds the matrix together although the pliablematerial could be a simple polymer or plastic material. An outer armorlayer 72 is an electrical isolation layer that also chemically protectsthe inner layers from treating fluids as well as wellbore fluids.

FIG. 5 depicts an alternative embodiment of a fiber encapsulated cable90. In this embodiment the fiber encapsulated cable 90 has a singleconductor 92. The conductor 92 may be metallic, electrically conductingfiber such as carbon fiber, or a fiber optic cable. The conductors 92may then be encapsulated in a pliable material 94. In many instances aresin is added to the pliable material 94, where the pliable material isa material such as chopped carbon fiber. The resin allows the pliablematerial 94 to harden thereby forming the fiber encapsulated materialinto a rod. An outer armor layer 96 that encapsulates the conductor 92and the pliable material 94 may be resin impregnated carbon fiber orsome other fiber as is known in the industry. In certain instances thepliable material 94 is not necessary and the conductor 92 may beencapsulated by only the outer armor layer 96.

The methods and materials described as being used in a particularembodiment may be used in any other embodiment. While the embodimentsare described with reference to various implementations andexploitations, it will be understood that these embodiments areillustrative and that the scope of the inventive subject matter is notlimited to them. Many variations, modifications, additions andimprovements are possible.

Plural instances may be provided for components, operations orstructures described herein as a single instance. In general, structuresand functionality presented as separate components in the exemplaryconfigurations may be implemented as a combined structure or component.Similarly, structures and functionality presented as a single componentmay be implemented as separate components. These and other variations,modifications, additions, and improvements may fall within the scope ofthe inventive subject matter.

What is claimed is:
 1. A fiber encapsulated cable for pipeline usecomprising: a pipeline having a central passageway, an opticalconductor, a carbon fiber sheath wrapped around the conductor; whereinthe carbon fiber sheath and the optical conductor are installed in thepipeline central passageway; and a remote monitoring station.
 2. Thefiber encapsulated cable for pipeline use of claim 1 wherein, the carbonfiber sheath has a coefficient of friction lower than the coefficient offriction of a metal encapsulated cable.
 3. The fiber encapsulated cablefor pipeline use of claim 1 wherein, the carbon fiber sheath is resinimpregnated.
 4. The fiber encapsulated cable for pipeline use of claim 1wherein, the conductor has a coating.
 5. The fiber encapsulated cablefor pipeline use of claim 4 wherein, the coating is an insulator.
 6. Thefiber encapsulated cable for pipeline use of claim 1 wherein, theconductor is at least a first conductor and a second conductor.
 7. Thefiber encapsulated cable for pipeline use of claim 6 wherein, the firstconductor is an electrical conductor.
 8. The fiber encapsulated cablefor pipeline use of claim 6 wherein, the second conductor is an opticalconductor.
 9. The fiber encapsulated cable for pipeline use of claim 1wherein, a filler separates the conductor from the carbon fiber sheath.10. The fiber encapsulated cable for pipeline use of claim 9 wherein,the filler is electrically conductive.
 11. The fiber encapsulated cablefor pipeline use of claim 9 wherein, the filler is electricallyinsulative.
 12. The fiber encapsulated cable for pipeline use of claim 1wherein, the fiber encapsulated cable is installed in the pipelinewithout pumping a fluid through the pipeline.
 13. A method of installinga fiber encapsulated cable in pipeline comprising: pulling a conductorinto a pipeline central passageway, wherein the conductor is wrapped ina carbon fiber sheath.
 14. The method of installing a fiber encapsulatedcable in pipeline of claim 13 wherein, the carbon fiber sheath has acoefficient of friction lower than the coefficient of friction of ametal encapsulated cable.
 15. The method of installing a fiberencapsulated cable in pipeline of claim 13 wherein, the carbon fibersheath is resin impregnated.
 16. The method of installing a fiberencapsulated cable in pipeline of claim 13 wherein, the conductor has acoating.
 17. The method of installing a fiber encapsulated cable inpipeline of claim 16 wherein, the coating is an insulator.
 18. Themethod of installing a fiber encapsulated cable in pipeline of claim 13wherein, the conductor is at least a first conductor and a secondconductor.
 19. The method of installing a fiber encapsulated cable inpipeline of claim 18 wherein, the first conductor is an electricalconductor.
 20. The method of installing a fiber encapsulated cable inpipeline of claim 18 wherein, the second conductor is an opticalconductor.
 21. The method of installing a fiber encapsulated cable inpipeline of claim 13 wherein, a filler separates the conductor from thecarbon fiber sheath.
 22. The method of installing a fiber encapsulatedcable in pipeline of claim 21 wherein, the filler is electricallyconductive.
 23. The method of installing a fiber encapsulated cable inpipeline of claim 21 wherein, the filler is an electrical insulator. 24.The method of installing a fiber encapsulated cable in pipeline of claim13 wherein, the fiber encapsulated cable is installed in the pipelinewithout pumping a fluid through the pipeline.
 25. A method of monitoringa pipeline comprising: installing a carbon fiber sheath and an opticalconductor along a pipeline; wherein the carbon fiber sheath is wrappedaround the optical conductor; and sensing a variation in the opticalconductor along a length of the pipeline.
 26. The method of monitoring apipeline of claim 25 wherein, the variation is a vibration.
 27. Themethod of monitoring a pipeline of claim 25 wherein, the variation is achange in temperature.
 28. The method of monitoring a pipeline of claim25 wherein, the variation is a change in pressure.
 29. The method ofmonitoring a pipeline of claim 25 further comprising supplyingelectrical power through the carbon fiber sheath.